Using Single-Row Functions to Customize Output. Copyright 2006, Oracle. All rights reserved.

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Using Single-Row Functions to

Customize Output

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Objectives

After completing this lesson, you should be able to do

the following:

• Describe various types of functions that are

available in SQL

• Use character, number, and date functions in

SELECT

statements

• Describe the use of conversion functions

Objectives

Functions make the basic query block more powerful, and they are used to manipulate data values. This is the first of two lessons that explore functions. It focuses on single-row character, number, and date functions, as well as those functions that convert data from one type to another (for example, conversion from character data to numeric data).

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SQL Functions

Function Input arg 1 arg 2 arg n Function performs action Output Result value SQL Functions

Functions are a very powerful feature of SQL. They can be used to do the following: • Perform calculations on data

• Modify individual data items

• Manipulate output for groups of rows • Format dates and numbers for display • Convert column data types

SQL functions sometimes take arguments and always return a value.

Note:Most of the functions that are described in this lesson are specific to the Oracle version of SQL.

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Two Types of SQL Functions

Single-row functions

Multiple-row functions Return one result

per row

Return one result per set of rows Functions

SQL Functions (continued) There are two types of functions:

• Single-row functions • Multiple-row functions

Single-Row Functions

These functions operate on single rows only and return one result per row. There are different types of single-row functions. This lesson covers the following ones:

• Character • Number • Date • Conversion • General Multiple-Row Functions

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Single-Row Functions

Single-row functions:

• Manipulate data items

• Accept arguments and return one value

• Act on each row that is returned

• Return one result per row

• May modify the data type

• Can be nested

• Accept arguments that can be a column or an

expression

function_name [(arg1, arg2,...)]

Single-Row Functions

Single-row functions are used to manipulate data items. They accept one or more arguments and return one value for each row that is returned by the query. An argument can be one of the following:

• User-supplied constant • Variable value

• Column name • Expression

Features of single-row functions include:

• Acting on each row that is returned in the query • Returning one result per row

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Single-Row Functions

Conversion Character Number Date General Single-row functions

Single-Row Functions (continued)

This lesson covers the following single-row functions:

• Character functions:Αccept character input and can return both character and number values

• Number functions:Accept numeric input and return numeric values

• Date functions:Operate on values of the DATEdata type (All date functions return a value of DATEdata type except the MONTHS_BETWEENfunction, which returns a number.) • Conversion functions:Convert a value from one data type to another

• General functions: - NVL - NVL2 - NULLIF - COALESCE - CASE

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Function Purpose

LOWER(column|expression) Converts alpha character values to lowercase

UPPER(column|expression) Converts alpha character values to uppercase

INITCAP(column|expression) Converts alpha character values to uppercase for the first letter of each word; all other letters in lowercase

Character Functions

Character functions LOWER UPPER INITCAP CONCAT SUBSTR LENGTH INSTR LPAD | RPAD TRIM REPLACE Case-manipulation functions Character-manipulation functions Character Functions

Single-row character functions accept character data as input and can return both character and numeric values. Character functions can be divided into the following:

• Case-manipulation functions • Character-manipulation functions

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Function Purpose

LENGTH(column|expression) Returns the number of characters in the expression

INSTR(column|expression, ’string’, [,m], [n] )

Returns the numeric position of a named string. Optionally, you can provide a position m to start searching, and the occurrence n of the string. m and n default to 1, meaning start the search at the beginning of the search and report the first occurrence.

LPAD(column|expression, n,

'string')

RPAD(column|expression, n,

'string')

Pads the character value right-justified to a total width of n

character positions

Pads the character value left-justified to a total width of n

character positions

TRIM(leading|trailing|both, trim_character FROM

trim_source)

Enables you to trim heading or trailing characters (or both) from a character string. If trim_character or

trim_source is a character literal, you must enclose it in single quotation marks.

This is a feature that is available in Oracle8i and later versions.

REPLACE(text, search_string, replacement_string)

Searches a text expression for a character string and, if found, replaces it with a specified replacement string

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Case-Manipulation Functions

These functions convert case for character strings:

sql course LOWER('SQL Course') Sql Course INITCAP('SQL Course') SQL COURSE UPPER('SQL Course') Result Function Case-Manipulation Functions

LOWER, UPPER, and INITCAPare the three case-conversion functions. • LOWER:Converts mixed-case or uppercase character strings to lowercase • UPPER:Converts mixed-case or lowercase character strings to uppercase

• INITCAP:Converts the first letter of each word to uppercase and remaining letters to lowercase

SELECT 'The job id for '||UPPER(last_name)||' is ' ||LOWER(job_id) AS "EMPLOYEE DETAILS"

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SELECT employee_id, last_name, department_id FROM employees

WHERE LOWER(last_name) = 'higgins';

Using Case-Manipulation Functions

Display the employee number, name, and department

number for employee Higgins:

SELECT employee_id, last_name, department_id FROM employees

WHERE last_name = 'higgins';

no rows selected

Using Case-Manipulation Functions

The slide example displays the employee number, name, and department number of employee Higgins.

The WHEREclause of the first SQL statement specifies the employee name as higgins. Because all the data in the EMPLOYEEStable is stored in proper case, the name higginsdoes not find a match in the table, and no rows are selected.

The WHEREclause of the second SQL statement specifies that the employee name in the

EMPLOYEEStable is compared to higgins, converting the LAST_NAMEcolumn to lowercase for comparison purposes. Because both names are now lowercase, a match is found and one row is selected. The WHEREclause can be rewritten in the following manner to produce the same result:

...WHERE last_name = 'Higgins'

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Character-Manipulation Functions

These functions manipulate character strings:

BLACK and BLUE REPLACE

('JACK and JUE','J','BL')

10 LENGTH('HelloWorld') 6 INSTR('HelloWorld', 'W') *****24000 LPAD(salary,10,'*') 24000***** RPAD(salary, 10, '*') HelloWorld CONCAT('Hello', 'World') elloWorld TRIM('H' FROM 'HelloWorld')

Hello SUBSTR('HelloWorld',1,5)

Result Function

Character-Manipulation Functions

CONCAT, SUBSTR, LENGTH, INSTR, LPAD, RPAD, and TRIMare the character-manipulation functions that are covered in this lesson.

• CONCAT:Joins values together (You are limited to using two parameters with CONCAT.) • SUBSTR:Extracts a string of determined length

• LENGTH:Shows the length of a string as a numeric value • INSTR:Finds the numeric position of a named character • LPAD:Pads the character value right-justified

• RPAD:Pads the character value left-justified

• TRIM:Trims heading or trailing characters (or both) from a character string (If

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SELECT employee_id, CONCAT(first_name, last_name) NAME, job_id, LENGTH (last_name),

INSTR(last_name, 'a') "Contains 'a'?" FROM employees

WHERE SUBSTR(job_id, 4) = 'REP';

Using the Character-Manipulation Functions

2

3

1

2

1

3

Using the Character-Manipulation Functions

The slide example displays employee first names and last names joined together, the length of the employee last name, and the numeric position of the letter ain the employee last name for all employees who have the string REPcontained in the job ID starting at the fourth position of the job ID.

Example

Modify the SQL statement in the slide to display the data for those employees whose last names end with the letter n.

SELECT employee_id, CONCAT(first_name, last_name) NAME, LENGTH (last_name), INSTR(last_name, 'a') "Contains 'a'?" FROM employees

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Number Functions

• ROUND

: Rounds value to specified decimal

• TRUNC

: Truncates value to specified decimal

• MOD

: Returns remainder of division

100 MOD(1600, 300)

45.93 ROUND(45.926, 2)

45.92 TRUNC(45.926, 2)

Result Function Number Functions

Number functions accept numeric input and return numeric values. This section describes some of the number functions.

Function Purpose

ROUND(column|expression, n) _{Rounds the column, expression, or value to n decimal} places or, if n is omitted, no decimal places (If n is

negative, numbers to left of the decimal point are rounded.) TRUNC(column|expression, n) _{Truncates the column, expression, or value to n decimal}

places or, if n is omitted, n defaults to zero MOD(m,n) _{Returns the remainder of m divided by n}

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SELECT ROUND(45.923,2), ROUND(45.923,0), ROUND(45.923,-1)

FROM DUAL;

Using the

ROUND

Function

DUAL

is a dummy table that you can use to view results

from functions and calculations.

3

1

2

1

2

ROUNDFunction

The ROUNDfunction rounds the column, expression, or value to ndecimal places. If the second argument is 0 or is missing, the value is rounded to zero decimal places. If the second argument is 2, the value is rounded to two decimal places. Conversely, if the second argument is –2, the value is rounded to two decimal places to the left (rounded to the nearest unit of 10).

The ROUNDfunction can also be used with date functions. You will see examples later in this lesson.

DUALTable

The DUALtable is owned by the user SYSand can be accessed by all users. It contains one column, DUMMY, and one row with the value X. The DUALtable is useful when you want to return a value once only (for example, the value of a constant, pseudocolumn, or expression that is not derived from a table with user data). The DUALtable is generally used for SELECTclause syntax completeness, because both SELECTand FROMclauses are mandatory, and several

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Using the

TRUNC

Function

SELECT TRUNC(45.923,2), TRUNC(45.923), TRUNC(45.923,-1) FROM DUAL;

3

1

2

1

2

TRUNCFunction

The TRUNCfunction truncates the column, expression, or value to n decimal places. The TRUNCfunction works with arguments similar to those of the ROUNDfunction. If the second argument is 0 or is missing, the value is truncated to zero decimal places. If the second argument is 2, the value is truncated to two decimal places. Conversely, if the second argument is –2, the value is truncated to two decimal places to the left. If the second argument is –1, the value is truncated to one decimal place to the left.

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SELECT last_name, salary, MOD(salary, 5000) FROM employees

WHERE job_id = 'SA_REP';

Using the

MOD

Function

For all employees with job title of Sales Representative,

calculate the remainder of the salary after it is divided by

5,000.

MODFunction

The MODfunction finds the remainder of the first argument divided by the second argument. The slide example calculates the remainder of the salary after dividing it by 5,000 for all employees whose job ID is SA_REP.

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SELECT last_name, hire_date FROM employees

WHERE hire_date < '01-FEB-88' ';';

Working with Dates

• The Oracle database stores dates in an internal numeric

format: century, year, month, day, hours, minutes, and

seconds.

• The default date display format is DD-MON-RR.

–

Enables you to store 21st-century dates in the

20th century by specifying only the last two digits of

the year

–

Enables you to store 20th-century dates in the

21st century in the same way

Oracle Date Format

The Oracle database stores dates in an internal numeric format, representing the century, year, month, day, hours, minutes, and seconds.

The default display and input format for any date is DD-MON-RR. Valid Oracle dates are between January 1, 4712 B.C., and December 31, 9999 A.D.

In the example in the slide, the HIRE_DATEcolumn output is displayed in the default format DD-MON-RR. However, dates are not stored in the database in this format. All the components of the date and time are stored. So, although a HIRE_DATEsuch as 17-JUN-87 is displayed as day, month, and year, there is also timeand centuryinformation associated with the date. The complete data might be June 17, 1987, 5:10:43 p.m.

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Oracle Date Format (continued) This data is stored internally as follows:

CENTURY YEAR MONTH DAY HOUR MINUTE SECOND

19 87 06 17 17 10 43

Centuries and the Year 2000

When a record with a date column is inserted into a table, the centuryinformation is picked up from the SYSDATEfunction. However, when the date column is displayed on the screen, the century component is not displayed (by default).

The DATEdata type always stores year information as a four-digit number internally: two digits for the century and two digits for the year. For example, the Oracle database stores the year as 1987 or 2004, and not just as 87 or 04.

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Working with Dates

SYSDATE

is a function that returns:

• Date

• Time

SYSDATEFunction

SYSDATEis a date function that returns the current database server date and time. You can use SYSDATEjust as you would use any other column name. For example, you can display the current date by selecting SYSDATEfrom a table. It is customary to select SYSDATEfrom a dummy table called DUAL.

Example

Display the current date using the DUALtable. SELECT SYSDATE

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Arithmetic with Dates

• Add or subtract a number to or from a date for a

resultant date value.

• Subtract two dates to find the number of days

between those dates.

• Add hours to a date by dividing the number of

hours by 24.

Arithmetic with Dates

Because the database stores dates as numbers, you can perform calculations using arithmetic operators such as addition and subtraction. You can add and subtract number constants as well as dates.

You can perform the following operations:

Operation Result Description

date + number Date Adds a number of days to a date date – number Date Subtracts a number of days from a date date – date Number of days Subtracts one date from another date + number/24 Date Adds a number of hours to a date

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SELECT last_name, (SYSDATE-hire_date)/7 AS WEEKS FROM employees

WHERE department_id = 90;

Using Arithmetic Operators

with Dates

Arithmetic with Dates (continued)

The example in the slide displays the last name and the number of weeks employed for all employees in department 90. It subtracts the date on which the employee was hired from the current date (SYSDATE) and divides the result by 7 to calculate the number of weeks that a worker has been employed.

Note:SYSDATEis a SQL function that returns the current date and time. Your results may differ from the example.

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Date Functions

Next day of the date specified NEXT_DAY

Last day of the month LAST_DAY

Round date ROUND

Truncate date TRUNC

Number of months between two dates MONTHS_BETWEEN

Add calendar months to date ADD_MONTHS

Result Function

Date Functions

Date functions operate on Oracle dates. All date functions return a value of DATEdata type except MONTHS_BETWEEN, which returns a numeric value.

• MONTHS_BETWEEN(date1, date2):Finds the number of months between date1 and date2. The result can be positive or negative. If date1is later than date2, the result is positive; if date1is earlier than date2, the result is negative. The noninteger part of the result represents a portion of the month.

• ADD_MONTHS(date, n):Adds nnumber of calendar months todate. The value ofn must be an integer and can be negative.

• NEXT_DAY(date, 'char'):Finds the date of the next specified day of the week ('char')following date. The value of charmay be a number representing a day or a character string.

• LAST_DAY(date):Finds the date of the last day of the month that contains date • ROUND(date[,'fmt']):Returns daterounded to the unit that is specified by the

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Using Date Functions

'08-SEP-95' NEXT_DAY ('01-SEP-95','FRIDAY') '28-FEB-95' LAST_DAY ('01-FEB-95') 19.6774194 MONTHS_BETWEEN ('01-SEP-95','11-JAN-94') '11-JUL-94' ADD_MONTHS ('11-JAN-94',6) Result Function

Date Functions (continued)

For example, display the employee number, hire date, number of months employed, six-month review date, first Friday after hire date, and last day of the hire month for all employees who have been employed for fewer than 80 months.

SELECT employee_id, hire_date,

MONTHS_BETWEEN (SYSDATE, hire_date) TENURE, ADD_MONTHS (hire_date, 6) REVIEW,

NEXT_DAY (hire_date, 'FRIDAY'), LAST_DAY(hire_date) FROM employees

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Using Date Functions

Assume

SYSDATE = '25-JUL-03'

:

01-JUL-03 TRUNC(SYSDATE ,'MONTH') 01-JAN-03 TRUNC(SYSDATE ,'YEAR') 01-AUG-03 ROUND(SYSDATE,'MONTH') 01-JAN-04 ROUND(SYSDATE ,'YEAR') Result Function

Date Functions (continued)

The ROUNDand TRUNCfunctions can be used for number and date values. When used with dates, these functions round or truncate to the specified format model. Therefore, you can round dates to the nearest year or month.

Example

Compare the hire dates for all employees who started in 1997. Display the employee number, hire date, and start month using the ROUNDand TRUNCfunctions.

SELECT employee_id, hire_date,

ROUND(hire_date, 'MONTH'), TRUNC(hire_date, 'MONTH') FROM employees

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Practice 3: Overview of Part 1

This practice covers the following topics:

• Writing a query that displays the current date

• Creating queries that require the use of numeric,

character, and date functions

• Performing calculations of years and months of

service for an employee

Practice 3: Overview of Part 1

Part 1 of this lesson’s practice provides a variety of exercises using different functions that are available for character, number, and date data types.

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Conversion Functions

Implicit data type conversion

Explicit data type conversion Data type

conversion

Conversion Functions

In addition to Oracle data types, columns of tables in an Oracle database can be defined using ANSI, DB2, and SQL/DS data types. However, the Oracle server internally converts such data types to Oracle data types.

In some cases, the Oracle server uses data of one data type where it expects data of a different data type. When this happens, the Oracle server can automatically convert the data to the expected data type. This data type conversion can be done implicitlyby the Oracle server or explicitlyby the user.

Implicit data type conversions work according to the rules that are explained in the next two slides.

Explicit data type conversions are done by using the conversion functions. Conversion functions convert a value from one data type to another. Generally, the form of the function names follows the convention data type TO data type. The first data type is the input data type; the

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Implicit Data Type Conversion

For assignments, the Oracle server can automatically

convert the following:

VARCHAR2 NUMBER VARCHAR2 DATE NUMBER VARCHAR2 or CHAR DATE VARCHAR2 or CHAR To From

Implicit Data Type Conversion

The assignment succeeds if the Oracle server can convert the data type of the value used in the assignment to that of the assignment target.

For example, the expression hire_date > '01-JAN-90'results in the implicit conversion from the string '01-JAN-90'to a date.

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Implicit Data Type Conversion

For expression evaluation, the Oracle Server can

automatically convert the following:

NUMBER VARCHAR2 or CHAR DATE VARCHAR2 or CHAR To From

Implicit Data Type Conversion (continued)

In general, the Oracle server uses the rule for expressions when a data type conversion is needed in places that are not covered by a rule for assignment conversions.

For example, the expression salary = '20000'results in the implicit conversion of the string '20000'to the number 20000.

Note:CHARto NUMBERconversions succeed only if the character string represents a valid number.

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Explicit Data Type Conversion

NUMBER

CHARACTER

TO_CHAR

TO_NUMBER

DATE

TO_CHAR

TO_DATE

Explicit Data Type Conversion

SQL provides three functions to convert a value from one data type to another:

Function Purpose

TO_CHAR(number|date,[ fmt],

[nlsparams]) Converts a number or date value to a VARCHAR2 character string with format model fmt

Number conversion: The nlsparams parameter specifies the following characters, which are returned by number format elements: • Decimal character

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Explicit Data Type Conversion

NUMBER

CHARACTER

TO_CHAR

TO_NUMBER

DATE

TO_CHAR

TO_DATE

Explicit Data Type Conversion (continued)

Function Purpose

TO_CHAR(number|date,[ fmt],

[nlsparams]) Date conversion: The nlsparams parameter specifies

the language in which month and day names and abbreviations are returned. If this parameter is omitted, this function uses the default date languages for the session.

TO_NUMBER(char,[fmt],

[nlsparams]) Converts a character string containing digits to a number

in the format specified by the optional format model fmt. The nlsparams parameter has the same purpose in this function as in the TO_CHAR function for number

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Explicit Data Type Conversion (continued)

Note:The list of functions mentioned in this lesson includes only some of the available conversion functions.

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Using the

TO_CHAR

Function with Dates

The format model:

• Must be enclosed by single quotation marks

• Is case sensitive

• Can include any valid date format element

• Has an

fm

element to remove padded blanks or

suppress leading zeros

• Is separated from the date value by a comma

TO_CHAR(date, 'format_model')

Displaying a Date in a Specific Format

Previously, all Oracle date values were displayed in the DD-MON-YY format. You can use the TO_CHARfunction to convert a date from this default format to one that you specify.

Guidelines

• The format model must be enclosed by single quotation marks and is case sensitive. • The format model can include any valid date format element. Be sure to separate the date

value from the format model by a comma.

• The names of days and months in the output are automatically padded with blanks. • To remove padded blanks or to suppress leading zeros, use the fill mode fmelement. • You can format the resulting character field with the iSQL*Plus COLUMNcommand

(covered in a later lesson).

SELECT employee_id, TO_CHAR(hire_date, 'MM/YY') Month_Hired FROM employees

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Elements of the Date Format Model

Three-letter abbreviation of the day of the week

DY

Full name of the day of the week DAY

Two-digit value for month MM

Full name of the month MONTH

Three-letter abbreviation of the month MON

Numeric day of the month DD

Full year in numbers YYYY

Year spelled out (in English) YEAR

Result Element

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Sample Format Elements of Valid Date Formats Element Description

SCC or CC Century; server prefixes B.C. date with - Years in dates YYYY or SYYYY Year; server prefixes B.C. date with - YYY or YY or Y Last three, two, or one digits of year Y,YYY Year with comma in this position

IYYY, IYY, IY, I Four-, three-, two-, or one-digit year based on the ISO standard

SYEAR or YEAR Year spelled out; server prefixes B.C. date with - BC or AD Indicates B.C. or A.D. year

B.C. or A.D. Indicates B.C. or A.D. year using periods Q Quarter of year

MM Month: two-digit value

MONTH Name of month padded with blanks to length of nine characters

MON Name of month, three-letter abbreviation RM Roman numeral month

WW or W Week of year or month DDD or DD or D Day of year, month, or week

DAY Name of day padded with blanks to a length of nine characters

DY Name of day; three-letter abbreviation

J Julian day; the number of days since December 31, 4713 B.C.

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Elements of the Date Format Model

• Time elements format the time portion of the date:

• Add character strings by enclosing them in double

quotation marks:

• Number suffixes spell out numbers:

DD "of" MONTH 12 of OCTOBER

ddspth fourteenth

HH24:MI:SS AM 15:45:32 PM

Date Format Elements: Time Formats

Use the formats that are listed in the following tables to display time information and literals and to change numerals to spelled numbers.

Element Description

AM or PM Meridian indicator

A.M. or P.M. Meridian indicator with periods

HH or HH12 or HH24 Hour of day, or hour (1–12), or hour (0–23) MI Minute (0–59)

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Other Formats

Specifying Suffixes to Influence Number Display Element Description

/ . , Punctuation is reproduced in the result. “of the” Quoted string is reproduced in the result.

Element Description

TH Ordinal number (for example, DDTH for 4TH) SP Spelled-out number (for example, DDSP for FOUR) SPTH or THSP Spelled-out ordinal numbers (for example, DDSPTH for

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SELECT last_name,

TO_CHAR(hire_date, 'fmDD Month YYYY') AS HIREDATE

FROM employees;

Using the

TO_CHAR

Function with Dates

…

Using the TO_CHARFunction with Dates

The SQL statement in the slide displays the last names and hire dates for all the employees. The hire date appears as 17 June 1987.

Example

Modify the slide example to display the dates in a format that appears as “Seventeenth of June 1987 12:00:00 AM.”

SELECT last_name, TO_CHAR(hire_date,

'fmDdspth "of" Month YYYY fmHH:MI:SS AM') HIREDATE

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Using the

TO_CHAR

Function with Numbers

These are some of the format elements that you can use

with the

TO_CHAR

function to display a number value as a

character:

Prints a decimal point .

Prints a comma as thousands indicator ,

Places a floating dollar sign $

Uses the floating local currency symbol L

Represents a number 9

Forces a zero to be displayed 0

Result Element

TO_CHAR(number, 'format_model')

Using the TO_CHARFunction with Numbers

When working with number values such as character strings, you should convert those numbers to the character data type using the TO_CHARfunction, which translates a value of NUMBER data type to VARCHAR2data type. This technique is especially useful with concatenation.

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Using the TO_CHARFunction with Numbers (continued)

Number Format Elements

If you are converting a number to the character data type, you can use the following format elements:

Element Description Example Result

9 Numeric position (number of 9s determine display width)

999999 1234 0 Display leading zeros 099999 001234 $ Floating dollar sign $999999 $1234 L Floating local currency symbol L999999 FF1234 D Returns in the specified position the decimal

character. The default is a period (.).

99D99 99.99 . Decimal point in position specified 999999.99 1234.00 G Returns the group separator in the specified

position. You can specify multiple group separators in a number format model.

9,999 9G999

, Comma in position specified 999,999 1,234 MI Minus signs to right (negative values) 999999MI 1234- PR Parenthesize negative numbers 999999PR <1234> EEEE Scientific notation (format must specify four Es) 99.999EEEE 1.234E+03 U Returns in the specified position the "Euro" (or

other) dual currency

U9999 €1234

V Multiply by 10 n times (n = number of 9s after V) 9999V99 123400 S Returns the negative or positive value S9999 -1234 or

+1234 B Display zero values as blank, not 0 B9999.99 1234.00

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SELECT TO_CHAR(salary, '$99,999.00') SALARY FROM employees

WHERE last_name = 'Ernst';

Using the

TO_CHAR

Function with Numbers

Guidelines

• The Oracle server displays a string of number signs (#) in place of a whole number whose digits exceed the number of digits that is provided in the format model.

• The Oracle server rounds the stored decimal value to the number of decimal places that is provided in the format model.

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Using the

TO_NUMBER

and

TO_DATE

Functions

• Convert a character string to a number format

using the

TO_NUMBER

function:

• Convert a character string to a date format using

the

TO_DATE

function:

• These functions have an

fx

modifier. This modifier

specifies the exact matching for the character

argument and date format model of a

TO_DATE

function.

TO_NUMBER(char[, 'format_model'])

TO_DATE(char[, 'format_model'])

Using the TO_NUMBERand TO_DATEFunctions

You may want to convert a character string to either a number or a date. To accomplish this task, use the TO_NUMBERor TO_DATEfunctions. The format model that you choose is based on the previously demonstrated format elements.

The fxmodifier specifies exact matching for the character argument and date format model of a TO_DATEfunction:

• Punctuation and quoted text in the character argument must exactly match (except for case) the corresponding parts of the format model.

• The character argument cannot have extra blanks. Without fx, Oracle ignores extra blanks. • Numeric data in the character argument must have the same number of digits as the

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Using the TO_NUMBERand TO_DATEFunctions (continued)

Example

Display the name and hire date for all employees who started on May 24, 1999. There are two spaces after the month Mayand the number 24in the following example. Because the fx modifier is used, an exact match is required and the spaces after the word Mayare not recognized:

SELECT last_name, hire_date FROM employees

WHERE hire_date = TO_DATE('May 24, 1999', 'fxMonth DD, YYYY'); *

WHERE hire_date = TO_DATE('May 24, 1999', 'fxMonth DD, YYYY') *

ERROR at line 3:

ORA-01858: a non-numeric character was found where a numeric was expected

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RR

Date Format

Current Year 1995 1995 2001 2001 Specified Date 27-OCT-95 27-OCT-17 27-OCT-17 27-OCT-95 RR Format 1995 2017 2017 1995 YY Format 1995 1917 2017 2095 If two digits of the current year are: 0–49 0–49 50–99 50–99

The return date is in the current century The return date is in the century after the current one

The return date is in the century before the current one The return date is in the current century If the specified two-digit year is:

RR

Date Format Element

The RRdate format is similar to the YYelement, but you can use it to specify different centuries. Use the RRdate format element instead of YYso that the century of the return value varies according to the specified two-digit year and the last two digits of the current year. The table in the slide summarizes the behavior of the RRelement.

Current Year Given Date Interpreted (RR) Interpreted (YY)

1994 _27-OCT-95 1995 1995 1994 _27-OCT-17 2017 1917 2001 _27-OCT-17 2017 2017

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Example of

RR

Date Format

To find employees hired before 1990, use the

RR

date

format, which produces the same results whether the

command is run in 1999 or now:

SELECT last_name, TO_CHAR(hire_date, 'DD-Mon-YYYY') FROM employees

WHERE hire_date < TO_DATE('01-Jan-90','DD-Mon-RR');

Example of

RR

Date Format

To find employees who were hired before 1990, the RRformat can be used. Because the current year is greater than 1999, the RRformat interprets the year portion of the date from 1950 to 1999.

The following command, on the other hand, results in no rows being selected because the YY format interprets the year portion of the date in the current century (2090).

SELECT last_name, TO_CHAR(hire_date, 'DD-Mon-yyyy') FROM employees

WHERE TO_DATE(hire_date, 'DD-Mon-yy') < '01-Jan-1990'; no rows selected

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Nesting Functions

• Single-row functions can be nested to any level.

• Nested functions are evaluated from the deepest level

to the least deep level.

F3(

F2

(

F1(col,arg1)

,

arg2

),arg3)

Step 1 = Result

1 Step 2 = Result

2 Step 3 = Result 3

Nesting Functions

Single-row functions can be nested to any depth. Nested functions are evaluated from the innermost level to the outermost level. Some examples follow to show you the flexibility of these functions.

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SELECT last_name,

UPPER(CONCAT(SUBSTR (LAST_NAME, 1, 8), '_US')) FROM employees

WHERE department_id = 60;

Nesting Functions

Nesting Functions (continued)

The slide example displays the last names of employees in department 60. The evaluation of the SQL statement involves three steps:

1. The inner function retrieves the first eight characters of the last name. Result1 = SUBSTR (LAST_NAME, 1, 8)

2. The outer function concatenates the result with _US. Result2 = CONCAT(Result1, '_US')

3. The outermost function converts the results to uppercase.

The entire expression becomes the column heading because no column alias was given.

Example

Display the date of the next Friday that is six months from the hire date. The resulting date should appear as Friday, August 13th, 1999. Order the results by hire date.

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General Functions

The following functions work with any data type and

pertain to using nulls:

• NVL (expr1, expr2)

• NVL2 (expr1, expr2, expr3)

• NULLIF (expr1, expr2)

• COALESCE (expr1, expr2, ..., expr

n

)

General Functions

These functions work with any data type and pertain to the use of null values in the expression list.

Function Description

NVL Converts a null value to an actual value

NVL2 If expr1 is not null, NVL 2 returns ex pr2. If e xpr1 is null, NVL2

returns e xpr3. The argum ent exp r1 can have any data type.

NULLIF Com pares two expressions and returns null if they are equal; returns the first expression if they are not equal

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NVL

Function

Converts a null value to an actual value:

• Data types that can be used are date, character,

and number.

• Data types must match:

–

NVL(commission_pct,0)

–

NVL(hire_date,'01-JAN-97')

–

NVL(job_id,'No Job Yet')

NVLFunction

To convert a null value to an actual value, use the NVL function.

Syntax

NVL (expr1, expr2) In the syntax:

• expr1is the source value or expression that may contain a null • expr2is the target value for converting the null

You can use the NVLfunction to convert any data type, but the return value is always the same as the data type of expr1.

NVLConversions for Various Data Types

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SELECT last_name, salary, NVL(commission_pct, 0),

(salary*12) + (salary*12*NVL(commission_pct, 0)) AN_SAL FROM employees;

Using the

NVL

Function

…

1

2

Using the NVLFunction

To calculate the annual compensation of all employees, you need to multiply the monthly salary by 12 and then add the commission percentage to the result:

SELECT last_name, salary, commission_pct,

(salary*12) + (salary*12*commission_pct) AN_SAL FROM employees;

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SELECT last_name, salary, commission_pct, NVL2(commission_pct,

'SAL+COMM', 'SAL') income

FROM employees WHERE department_id IN (50, 80);

Using the

NVL2

Function

1

2

1

Using the NVL2Function

The NVL2function examines the first expression. If the first expression is not null, then the NVL2function returns the second expression. If the first expression is null, then the third expression is returned.

Syntax

NVL2(expr1, expr2, expr3) In the syntax:

• expr1is the source value or expression that may contain null • expr2is the value that is returned if expr1is not null • expr3is the value that is returned if expr1is null

In the example shown in the slide, the COMMISSION_PCTcolumn is examined. If a value is detected, the second expression of SAL+COMMis returned. If the COMMISSION_PCTcolumn holds a null value, the third expression of SALis returned.

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SELECT first_name, LENGTH(first_name) "expr1", last_name, LENGTH(last_name) "expr2",

NULLIF(LENGTH(first_name), LENGTH(last_name)) result FROM employees;

Using the

NULLIF

Function

…

1

2

3

1

2

3

Using the NULLIFFunction

The NULLIFfunction compares two expressions. If they are equal, the function returns null. If they are not equal, the function returns the first expression. You cannot specify the literal NULL for the first expression.

Syntax

NULLIF (expr1, expr2) In the syntax:

• expr1is the source value compared to expr2

• expr2is the source value compared with expr1(If it is not equal to expr1, expr1is returned.)

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Using the

COALESCE

Function

• The advantage of the

COALESCE

function over the

NVL

function is that the

COALESCE

function can

take multiple alternate values.

• If the first expression is not null, the

COALESCE

function returns that expression; otherwise, it does

a

COALESCE

of the remaining expressions.

Using the COALESCEFunction

The COALESCE function returns the first non-null expression in the list.

Syntax

COALESCE (expr1, expr2, ... exprn) In the syntax:

• expr1returns this expression if it is not null

• expr2returns this expression if the first expression is null and this expression is not null • exprnreturns this expression if the preceding expressions are null

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Using the

COALESCE

Function

…

Using the COALESCEFunction (continued)

In the example shown in the slide, if the MANAGER_IDvalue is not null, it is displayed. If the MANAGER_IDvalue is null, then the COMMISSION_PCTis displayed. If the MANAGER_ID and COMMISSION_PCTvalues are null, then the value –1 is displayed.

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Conditional Expressions

• Provide the use of IF-THEN-ELSE logic within a SQL

statement

• Use two methods:

–

CASE

expression

–

DECODE

function

Conditional Expressions

Two methods used to implement conditional processing (IF-THEN-ELSE logic) in a SQL statement are the CASEexpression and the DECODEfunction.

Note:The CASEexpression complies with ANSI SQL. The DECODEfunction is specific to Oracle syntax.

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CASE

Expression

Facilitates conditional inquiries by doing the work of an

IF-THEN-ELSE statement:

CASE expr WHEN comparison_expr1 THEN return_expr1 [WHEN comparison_expr2 THEN return_expr2 WHEN comparison_exprn THEN return_exprn ELSE else_expr]

END

CASEExpression

CASEexpressions let you use IF-THEN-ELSE logic in SQL statements without having to invoke procedures.

In a simple CASEexpression, the Oracle server searches for the first WHEN ... THENpair for which expris equal to comparison_exprand returns return_expr. If none of the WHEN ... THENpairs meet this condition, and if an ELSEclause exists, then the Oracle server returns else_expr. Otherwise, the Oracle server returns null. You cannot specify the literal NULLfor all the return_exprs and the else_expr.

All of the expressions ( expr, comparison_expr, and return_expr) must be of the same data type, which can be CHAR, VARCHAR2, NCHAR, or NVARCHAR2.

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SELECT last_name, job_id, salary,

CASE job_id WHEN 'IT_PROG' THEN 1.10*salary WHEN 'ST_CLERK' THEN 1.15*salary WHEN 'SA_REP' THEN 1.20*salary ELSE salary END "REVISED_SALARY" FROM employees;

Using the

CASE

Expression

Facilitates conditional inquiries by doing the work of an

IF-THEN-ELSE statement:

…

Using the CASEExpression

In the SQL statement in the slide, the value of JOB_IDis decoded. If JOB_IDis IT_PROG, the salary increase is 10%; if JOB_IDis ST_CLERK, the salary increase is 15%; if JOB_IDis SA_REP, the salary increase is 20%. For all other job roles, there is no increase in salary. The same statement can be written with the DECODEfunction.

This is an example of a searched CASEexpression. In a searched CASEexpression, the search occurs from left to right until an occurrence of the listed condition is found, and then it returns the return expression. If no condition is found to be true, and if an ELSEclause exists, the return expression in the ELSEclause is returned; otherwise, NULLis returned.

SELECT last_name,salary,

(CASE WHEN salary<5000 THEN 'Low' WHEN salary<10000 THEN 'Medium' WHEN salary<20000 THEN 'Good' ELSE 'Excellent'

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DECODE

Function

Facilitates conditional inquiries by doing the work of a

CASE

expression or an IF-THEN-ELSE statement:

DECODE(col|expression, search1, result1

[, search2, result2,...,] [, default])

DECODEFunction

The DECODEfunction decodes an expression in a way similar to the IF-THEN-ELSE logic that is used in various languages. The DECODEfunction decodes expressionafter comparing it to each searchvalue. If the expression is the same as search, resultis returned.

If the default value is omitted, a null value is returned where a search value does not match any of the result values.

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SELECT last_name, job_id, salary,

DECODE(job_id, 'IT_PROG', 1.10*salary, 'ST_CLERK', 1.15*salary, 'SA_REP', 1.20*salary, salary)

REVISED_SALARY FROM employees;

Using the

DECODE

Function

…

Using the DECODEFunction

In the SQL statement in the slide, the value of JOB_IDis tested. If JOB_IDis IT_PROG, the salary increase is 10%; if JOB_IDis ST_CLERK, the salary increase is 15%; if JOB_IDis SA_REP, the salary increase is 20%. For all other job roles, there is no increase in salary. The same statement can be expressed in pseudocode as an IF-THEN-ELSE statement:

IF job_id = 'IT_PROG' THEN salary = salary*1.10 IF job_id = 'ST_CLERK' THEN salary = salary*1.15 IF job_id = 'SA_REP' THEN salary = salary*1.20 ELSE salary = salary

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SELECT last_name, salary,

DECODE (TRUNC(salary/2000, 0), 0, 0.00, 1, 0.09, 2, 0.20, 3, 0.30, 4, 0.40, 5, 0.42, 6, 0.44, 0.45) TAX_RATE FROM employees WHERE department_id = 80;

Using the

DECODE

Function

Display the applicable tax rate for each employee in

department 80:

Using the DECODEfunction (continued)

This slide shows another example using the DECODEfunction. In this example, you determine the tax rate for each employee in department 80 based on the monthly salary. The tax rates are as follows:

Monthly Salary Range Tax Rate

$0.00–1,999.99 00% $2,000.00–3,999.99 09% $4,000.00–5,999.99 20% $6,000.00–7,999.99 30% $8,000.00–9,999.99 40%

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Summary

In this lesson, you should have learned how to:

• Perform calculations on data using functions

• Modify individual data items using functions

• Manipulate output for groups of rows using

functions

• Alter date formats for display using functions

• Convert column data types using functions

• Use

NVL

functions

• Use IF-THEN-ELSE logic

Summary

Single-row functions can be nested to any level. Single-row functions can manipulate the following:

• Character data: LOWER, UPPER, INITCAP, CONCAT, SUBSTR, INSTR, LENGTH • Number data: ROUND, TRUNC, MOD

• Date data: MONTHS_BETWEEN, ADD_MONTHS, NEXT_DAY, LAST_DAY, ROUND, TRUNC Remember the following:

• Date values can also use arithmetic operators.

• Conversion functions can convert character, date, and numeric values: TO_CHAR, TO_DATE, TO_NUMBER

• There are several functions that pertain to nulls, including NVL, NVL2, NULLIF, and COALESCE.

• IF-THEN-ELSE logic can be applied within a SQL statement by using the CASEexpression or the DECODEfunction.

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Practice 3: Overview of Part 2

This practice covers the following topics:

• Creating queries that require the use of numeric,

character, and date functions

• Using concatenation with functions

• Writing non-case-sensitive queries to test the

usefulness of character functions

• Performing calculations of years and months of

service for an employee

• Determining the review date for an employee

Practice 3: Overview of Part 2

Part 2 of this lesson’s practice provides a variety of exercises using different functions that are available for character, number, and date data types. For Part 2, complete exercises 7–14.

Remember that for nested functions, the results are evaluated from the innermost function to the outermost function.

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…

Practice 3

Part 1

1. Write a query to display the current date. Label the column Date.

2. The HR department needs a report to display the employee number, last name, salary, and salary increased by 15.5% (expressed as a whole number) for each employee. Label the column New Salary. Place your SQL statement in a text file named lab_03_02.sql.

3. Run your query in the file lab_03_02.sql.

4. Modify your query lab_03_02.sqlto add a column that subtracts the old salary from the new salary. Label the column Increase. Save the contents of the file as

lab_03_04.sql. Run the revised query.

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Practice 3 (continued)

5. Write a query that displays the last name (with the first letter uppercase and all other letters lowercase) and the length of the last name for all employees whose name starts with the letters J, A,or M. Give each column an appropriate label. Sort the results by the employees’ last names.

Rewrite the query so that the user is prompted to enter a letter that starts the last name. For example, if the user enters

H

when prompted for a letter, then the output should show all employees whose last name starts with the letter H.

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6. The HR department wants to find the length of employment for each employee. For each employee, display the last name and calculate the number of months between today and the date on which the employee was hired. Label the column MONTHS_WORKED. Order your results by the number of months employed. Round the number of months up to the closest whole number.

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Part 2

7. Create a report that produces the following for each employee:

<employee last name> earns <salary> monthly but wants <3 times salary>. Label the column Dream Salaries.

If you have time, complete the following exercises:

8. Create a query to display the last name and salary for all employees. Format the salary to be 15 characters long, left-padded with the $ symbol. Label the column SALARY.

…

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9. Display each employee’s last name, hire date, and salary review date, which is the first Monday after six months of service. Label the column REVIEW. Format the dates to appear in the format similar to “Monday, the Thirty-First of July, 2000.”

10. Display the last name, hire date, and day of the week on which the employee started. Label the column DAY. Order the results by the day of the week, starting with Monday.

…

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If you want an extra challenge, complete the following exercises:

11. Create a query that displays the employees’ last names and commission amounts. If an employee does not earn commission, show “No Commission.” Label the column COMM.

12. Create a query that displays the first eight characters of the employees’ last names and indicates the amounts of their salaries with asterisks. Each asterisk signifies a thousand dollars. Sort the data in descending order of salary. Label the column

EMPLOYEES_AND_THEIR_SALARIES.

…

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13. Using the DECODEfunction, write a query that displays the grade of all employees based on the value of the column JOB_ID, using the following data:

Job Grade AD_PRES A ST_MAN B IT_PROG C SA_REP D ST_CLERK E